Above, some_creation_function() will be called
when Dogpile.acquire() is first called. The
remainder of the with block then proceeds. Concurrent threads which
call Dogpile.acquire() during this initial period
will be blocked until some_creation_function() completes.

Once the creation function has completed successfully the first time,
new calls to Dogpile.acquire() will call some_creation_function()
each time the "expiretime" has been reached, allowing only a single
thread to call the function. Concurrent threads
which call Dogpile.acquire() during this period will
fall through, and not be blocked. It is expected that
the "stale" version of the resource remain available at this
time while the new one is generated.

dogpile.core is at the core of the dogpile.cache package
which provides for a basic cache API and sample backends based on the dogpile concept.

Development Status

dogpile.core has been in use in a small number of production environments for a period of
months, and as of 0.3.2 has entered beta status. No issues have been reported yet with its
core synchronization model, and overall the project hasn't seen many changes.
Most development continues within dogpile.cache.